One type of gas discharge light source used in photolithography is known as an excimer light source or laser. An excimer laser typically uses a combination of a noble gas, such as argon, krypton, or xenon, and a reactive such as fluorine or chlorine. The excimer laser derives its name from the fact that under the appropriate condition of electrical stimulation (energy supplied) and high pressure (of the gas mixture), a pseudo-molecule called an excimer is created, which only exists in an energized state and gives rise to amplified light in the ultraviolet range.
Excimer light sources are used in photolithography machines. The excimer light source produces deep ultraviolet (DUV) light. An excimer light source can be built using a single gas discharge chamber or using a plurality of gas discharge chambers.